Magnetic reed proximity switch



June 1, 1955 R. c. HESS 3,187,127

MAGNETIC REED PROXIMITY SWITCH Filed Jan. 9, 1962 50 r i 10 52 I 3 N 36II 12 5 v INVENTOR. H Q Bafzard 6. Hess Ti 12 BY g [1/1. W

111. HII'OHNL'Y United States Patent "ce 3,187,127 MAGNETIC REEDPRQXIMITY SWITCH Richard C. Hess, Monroeville, Pa., assignor toWestinghouse Air Brake Company, Wilmerding, Pa., a corporation ofPennsylvania Filed Jan. 9, 1962, Ser. No. 165,144 3 Claims. (Cl.200-6141) This invention relates to proximity detectors and, moreparticularly, to a detector which is influenced by the wheels of cars ortrains passing along the rail.

Proximity detectors of the type comprehended by this invention findapplication in a variety of fields, notably in railway car detection andsignaling systems. They comprise basically a magnetized assemblyassociated with the rail structure. This assembly usually includes amagnetized element mounted on one of the rails to form a magneticcircuit having a gap through which the wheels of a moving car pass andin so doing modify the condition of the circuit. This change in thecondition of the circuit is, in turn, detected by various types ofelements or devices which serve to actuate appropriate recording and/ orindicating units.

In the fields of application of such devices, a number of factors are ofmajor importance in determining the practical utility and economicsuitability of the device. For example, among these important factorsare small size, simplicity of structure, low manufacturing cost, facility of assembly and disassembly as for repair, replacement andmaintenance. Prior art structures are not entirely satisfactory from thestandpoints indicated.

One general object of this invention is to improve proximity detectorsof the type noted.

More specifically, objects of this invention are to reduce the size ofsuch devices, simplify the structure thereof, reduce the manufacturingcost, and enable ready assembly and disassembly.

A still further objective of this invention is to provide a magneticallyoperated proximity detector, the operation of which is independent ofthe speed of the object to be detected.

Generally speaking, the proximity detector embodying this invention,which is responsive to a passing permeable object, consists of amagnetically operated switch mounted in spaced relation to a source ofmagnetic flux which is arranged to project a first portion of its fieldinto the path of the passing object and a second portion of its fieldthrough the magnetic contacting members of the switch, urging thecontacting members into a closed actuated position during the absence ofa permeable object within the first portion of the magnetic field.However, when the passing permeable object is within the first portionof the magnetic field, the second portion of the field is shifted awayfrom the contacting members of the switch and toward the permeableobject, thereby allowing the contacting members to assume an opendeactuated position.

Other objects, purposes and characteristic features of my invention willbecome, in part, obvious from the accompanying drawings and, in part,pointed out as the description of my invention progresses, and referenceis made to the accompanying drawings, in which similar referencecharacters refer to corresponding parts throughout the several views,and in which:

FIG. 1 is a perspective view of a rail onto which an embodiment of theinvention has been mounted, with portions broken away to illustrate tobetter advantage certain details of construction;

FIG. 2 is a plan view showing a modification of the detector illustratedin FIG. 1, and

FIG. 3 is a plan view of another modification of the illustrativeembodiment shown in FIG. 1.

The apparatus shown in connection with FIG. 1 re- 3, l 811i 2 7 Estein-ed June 1 1 965 lates to railway systems and the control oftralfic thereon. However, it should be understood that the principles ofthe invention are of general application and their association withrailway systems is shown only as a matter of convenience.

Referring to the constructional details shown in FIG. 1, the proximitydetector 10 of the present invention is shown positioned adjacent theweb of a rail 12 and is operated by the flange portion of wheel 14 of apassing railway vehicle.

The detector of the present invention is shown fixedly mounted on aninverted L-shaped bracket 16, the vertical leg of which is adjustablysecured to the web portion of rail 12 by bolts 13 which pass throughelongated openings 2% in bracket 16.

As shown, detector It is mounted on the horizontal leg of bracket 16 andis enclosed Within a nonmagnetic housing 22 which is substantially waterand dust proof.

The elements within housing 22 which make up the detector of thisinvention are shown mounted in spaced relation on a base 24, and consistof a U-shaped magnet 26 and a switch 23 fixedly mounted on theupstanding portion of an L-shaped bracket 3d, formed of a nonmagneticmaterial such as brass, which is adjustably secured to base 24 by meansof screw 32.

In the embodiment of the invention shown for illustra tive purposes, thebight portion of magnet 26 is shown secured to base 24, as by weldingfor example, with its leg portions projecting upwardly. As a result, themain field of the magnet curves upwardly from one leg of the magnet tothe other toward the head of rail 12 with a portion of the fringe areaof the main field extending horizontally through switch 28. Preferablythe magnet used is of permanently magnetizable material capable of beingvery strongly magnetized and having a high degree of retentivity. Anexample of a material which has these qualifications is the alloy ofaluminum, nickel and cobalt sold commercially under the trade nameAlnico.

The switch 28 is a well-known type of magnetically controlled switchingdevice, which generally takes the form of a cylindrical enclosure 34 ofelectrically insulatin nonmagnetic material such as glass, surrounding apair of reeds or electrical contacting members 36 extending into theenclosure 34 from opposite ends. Reeds 36, which are of magneticmaterial such as soft iron and may have precious metal contact surfaces,are positioned to overlap at their spaced inner extremities, the innerextremities, however, being normally biased apart by a small distance.Leads 38 are secured, as by soldering, to the outer extremities of reeds36 and extend through housing 22 to an appropriate counting circuitand/or indicating device (not shown).

in accordance with the operation of the preferred embodiment of theproximity detector illustrated and described herein, switch 23 isadjusted and positioned on base 24 with respect to magnet 26 so thatreeds 36 are in the path of the horizontal portion of the fringe area ofthe magnetic flux field established by magnet 26 so as to influence andthereby cause reeds 36 to close in the absence of permeable materialwithin the main field of magnet as and to open during the presence ofpermeable material within the main field. This adjustment is made byvertical manipulation of detector 1%) along the web of rail 12 andhorizontal manipulation of switch 28 on base 24. When this adjustment isachieved, further vertical movement of detector 10 is prevented bytightening bolts 18 against bracket 16, and further horizontal movementof switch 23 is prevented by fixedly securing bracket 3% to base 24 bytightening screw 32.

When the proximity detector of the present invention has been mountedand adjusted in the manner shown described, a magnetic circuit may thenbe traced, in the absence of permeable material in the main field,between magnet 26 and switch 23, from one leg of magnet 26 across theair gap separating the elements, through reeds 3 6 and back through theair gap to the opposite leg of magnet 26. As a result of thisarrangement and adjustment, reeds 36 of switch 23 are actuated to aclosed, energized position.

When a permeable material, such as the flange of wheel li iof a railwayvehicle, is within the upwardly projecting main field of the magnet, theiiux in the main field is increased because of the lower reluctance inthe upper path, thereby shifting and weakening the strength of thehorizontal fringe area through reeds 36 of switch 215 and allowing themto separate. The resulting interruption of current flow through switch28 can then be detected by an appropriate indicating and/or recordingdevice (not shown).

As wheel 14 moves along rail 12 and away from detector iii, the fringearea of the main magnetic field again shifts back to influence andthereby close reeds 36 of switch 2%.

The illustrative embodiment of the invention just described and shown inFIG. 1 discloses a detector having reeds or contacts normally actuatedto a closed condition in the absence of permeable material. arrangementsutilizing the underlying principles of construction and operation ofthis invention are possible and, dependin upon the particularcircumstances, perhaps even preferable.

Thus, for example, HG. 2 shows an arrangement wherein the position ofthe elements in detector 10 are just the reverse of that shown inPEG. 1. in other words, in this modification, switch is positioned onbase 24- between rail 12 and magnet 26.

FIG. 3 illustrates another modification of the proximity detectordescribed above which has a switch having reeds or contacts normallyactuated to an open position in the absence of permeable material. Thearrangement of the elements within the modified detector illustrated inFIG. 3 is substantially the same as that shown and described withrespect to FIG. 1. However, in order to provide a detector with anormally open switch in the absence of a permeable object, a smallpermanent magnet 40, preferably U-shaped, is positioned adjacent switch28 with its pole pieces projecting upwardly and arranged so that itspolarity arrangement is the reverse of magnet 26. The strength of theflux field of magnet should be sulficient to close reeds 36 when thefringe area of the main field of stronger magnet 26 is shifted and thusweakened during the presence of permeable material. In addition, switchH 2%; is so positioned on base 24 that the influence of magnets 2i'; and40 on the switch offset each other and thereby allow reeds 36 to remainseparated during the absence of permeable material within the main fieldabove magnet 26. By having magnet 26 considerably stronger than magnet40, a gap between magnet 26 and switch 28 may be provided to facilitateaccurate adjustments without af ecting the offsetting influence eachmagnet has on the other with respect to the switch.

When the permeable object to be detected is within the main upwardlyprojecting field of magnet 26, the weakening of its horizontal fringearea through switch 23 enables the weaker magnet ll) to close the reeds36 of switch 28. When the permeable object passes and is no longerwithin the main field of magnet 26, the horizontal fringe area of themain flux field of the stronger magnet 26 then shifts back through theswitch and again offsets the influence of magnet 40, thereby enablingthe reeds 36 of switch 23 to separate.

As is apparent from the foregoing description, no source of power isrequired to control the operation of the detector. Furthermore, with theexception of reeds 36, there are no moving parts in the detector to wearout. Also, as a result of the comparatively high power handlingcapabilities of reed switches, no power amplification is gen- However,other erally required when the track instrument is used to drive otherapparatus.

Although the present invention provides an instrument for, in effect,counting the axles of railway cars, it is to be understood that thisform is selected to facilitate the disclosure of the invention and isnot intended to limit the number of applications in which it may beemployed. Moreover, it is to be further understood that variousmodifications, adaptations and alterations may be applied to thespecific forms shown to meet the requirements of practice, without inany manner departing from the spirit or scope of the present invention.

Having thus described my invention, what I claim is:

1. A device responsive to the presence at a point along a predeterminedpath of a passing permeable object comprising, a housing includinga'base mounted adjacent said point, a U-shaped magnet mounted on saidbase and arranged to project its main flux field in an upwardlydirection from said base into the path of said object, with a portion ofthe fringe area of said field extending horizontally from said magnetduring the absence of a permeable object within said main field, abracket mounted on said base in spaced relation to said magnet, and amagnetically operated switch secured to said bracket in juxtaposedreiation to said U-shape magnet and actuated to a first condition whenwithin a portion of the fringe area of said main field and to a secondcondition when without the fringe area of said field.

2. A device for detecting a permeable object passing along apredetermined path comprising, a base securely fastened adjacent saidpath, a magnetically operated switch mounted on said base and having afirst actuated condition and a second biased condition, a U-shapedmagnet positioned in juxtaposed relation to said switch and having itsbight portion secured to said base with its legs extending upwardlytherefrom projecting its main flux field into the path of said permeableobject with a portion of the fringe area of said main field extendingthrough and influencing said switch to a first condition during theabsence of permeable material in said main field, said fringe areashifting away from said switch during the presence of permeable materialin said main field enabling said switch to assume its second biasedcondition.

3. A device responsive to the presence at a point along a predeterminedpath of a passing permeable object comprising, a base mounted adjacentsaid point, a bracket adjustably mounted on said base, a magneticallyoperated switch secured to said bracket with its longitudinal axissubstantially parallel to said base and actuable to a first conditionand biased to a second condition, a U-shaped magnet positioned injuxtaposed relation to said switch and having its bight portion securedto said base with its leg portions extending upwardly therefromprojecting its main field into the path of said object with a portion ofthe fringe area of said field extending through and influencing saidswitch to its first condition during the absence of a permeable objectin said main field, said fringe area being shifted away from said switchduring the presence of said permeable object in said main field allowingsaid switch to assume a second biased condition.

References Qited by the Examiner UNITED STATES PATENTS BERNARD A.GILHEANY, Primary Examiner.

1. A DEVICE RESPONSIVE TO THE PRESENCE AT A POINT ALONG A PREDETERMINEDPATH OF A PASSING PERMEABLE OBJECT COMPRISING, A HOUSING INCLUDING ABASE MOUNTED ADJACENT SAID POINT, A U-SHAPED MAGNET MOUNTED ON SAID BASEAND ARRANGED TO PROJECT ITS MAIN FLUX FIELD IN AND UPWARDLY DIRECTIONFROM SAID BASE INTO THE PATH OF THE SAID OBJECT, WITH A PORTION OF THEFRINGE AREA OF SAID FIELD EXTENDING HORIZONTALLY FROM SAID MAGNET DURINGTHE ABSENCE OF A PERMEABLE OBJECT WITHIN SAID MAIN FIELD, A BRACKETMOUNTED ON SAID BASE IN SPACED RELATION TO SAID MAGNET, AND AMAGNETICALLY OPERATED SWITCH SECURED TO SAID BRACKET IN JUXTAPOSEDRELATION TO SAID U-SHAPE MAGNET AND ACTUATED TO A FIRST CONDITION WHENWITHIN A PORTION OF THE FRINGE AREA OF SAID MAIN FIELD AND TO A SECONDCONDITION WHEN WITHOUT THE FRINGE AREA OF SAID FIELD.